Uniformly Sized Stem Cell Spheroids for Treatment of Hind Limb Ischemia: Size Effect

Abstract

Spheroid‐based cell delivery has been demonstrated as an effective strategy in stem cell therapy of critical limb ischemia. However, massive generation of uniform‐sized spheroids still remains a big challenge. In addition, how spheroid size influences its therapeutic efficacy remains an open question. Herein, patterned poly(2‐hydroxyethyl methacrylate) hydrogel films synthesized in situ in cell culture plates are used to generate adipose‐derived stromal cell (ADSC) spheroids. This method not only allows for the production of uniform‐sized spheroids but also large‐scale production (≈60 000 spheroids per plate). Using this method, monodisperse ADSC spheroids with three different sizes are generated to study spheroid size effect in ischemia treatment. It is found that different size spheroids exhibit different behaviors in extracellular matrix (ECM) expression and paracrine secretion. Larger spheroids express more ECM proteins. Paracrine secretion of hypoxia‐induced survival factors, anti‐apoptotic and angiogenic factors is enhanced to a larger degree in larger spheroids. Finally, using a mouse model of hind limb ischemia, it is demonstrated that the therapeutic efficacy of the spheroids increases with increasing spheroid size. The improved therapeutic efficacy is attributed to enhanced survival and paracrine secretion of larger spheroids, which is attributed to the higher degree of hypoxic environment of these spheroids.

The Transplantation of 3-Dimensional Spheroids of Adipose-Derived Stem Cells Promotes Achilles Tendon Healing in Rabbits by Enhancing the Proliferation of Tenocytes and Suppressing M1 Macrophages

“…First, the size of the ADSC spheroids was not optimized in the present study. As previously reported, 1,7,17,40 stem cell spheroids with different sizes exhibit various therapeutic potentials, as spheroid size significantly affects inherent niches (concentrations of oxygen, nutrients, and metabolic waste) and thus the metabolic configuration and activity of the cells grown within the spheroids. Therefore, the spheroid size for each stem cell source should be optimized before further use.…”

Schwann cells acquire a repair phenotype after assembling into spheroids and show enhanced in vivo therapeutic potential for promoting peripheral nerve repair

“…It is well established that spheroid sizes are closely linked to the microenvironments within the spheroid interior, influencing cellular behaviors and thus therapeutic potential. 41,[71][72][73] Therefore, further research aimed at determining the optimal size of SC spheroids should be conducted before their broader application. Fourth, the phenotype of both the engrafted and endogenous SCs throughout the nerve repair process was not monitored.…”

“…Third, the size of the SC spheroids prepared in the present study was not optimized. It is well established that spheroid sizes are closely linked to the microenvironments within the spheroid interior, influencing cellular behaviors and thus therapeutic potential 41,71–73 . Therefore, further research aimed at determining the optimal size of SC spheroids should be conducted before their broader application.…”

Anthracene dimer cross-linked, washing- and sterilization-free hydrogel films for multicellular spheroid generation

“…24 Recently this method was used for massive production of uniform-sized stem cell spheroids, which were demonstrated to have high potential in the treatment of hind limb ischemia. 28…”

“…24 Recently this method was used for massive production of uniform-sized stem cell spheroids, which were demonstrated to have high potential in the treatment of hind limb ischemia. 28 The PHEMA hydrogel films were synthesized by UV curing of a prepolymer mixture containing the HEMA monomer, a crosslinker and a photo-initiator, 24 and linear PHEMA when using a one-step UV curing method, 29 or by bulk redox polymerization of a mixture containing the HEMA monomer, a cross-linker and a redox initiator. 30 In these methods, one should adjust carefully the formula of the prepolymer mixture to obtain hydrogel films with a smooth surface, which is a requisite for the following swelling-induced patterning.…”